Conventionally, a technique of implementing so-called idling stop control of automatically stopping an engine if predetermined automatic stop conditions are fulfilled, and, thereafter, restarting the engine if predetermined restart conditions are fulfilled, is known.
When an engine is automatically stopped, an opening degree of a throttle valve is made smaller than a predetermined opening degree, so that supply of air to a cylinder is restricted. However, in such a case, when the engine restarts, a sufficient amount of air cannot be secured for combustion, which may lead to worse restart.
In the technique disclosed in PTL 1, control is performed so that an opening degree of a throttle valve is made smaller than a predetermined opening degree when an engine is automatically stopped, and, if engine speed becomes equal to or less than a predetermined value, the throttle valve which has been closed is once opened to more than the predetermined opening degree, and then, is closed again. By this means, a minimum required amount of air for restarting the engine is secured, to alleviate delay when the engine restarts.